1. Field of Invention
The present invention relates to a fabricating method of a light emitting diode (LED) package structure. More particularly, the present invention relates to a fabricating method of an LED package structure with integration of a thermoelectric cooling device.
2. Description of Related Art
The LED is a semiconductor element, and the material of the light-emitting chip mainly employs one selected from group III-V chemical elements such as GaP, GaAs, GaN, and other compound semiconductors. The light emitting principle is converting electric energy into light, i.e., applying current to the compound semiconductor, such that redundant energy is released in a form of light through the combination of electrons and electron holes, thus achieving the light emitting effect. Since the light emitting phenomenon of the LED is not caused by heating or discharging, the LED is a cold light emitting diode, and thus the service life of the LED may be more than 100,000 hours, and idling time is saved. Further, the LED has the advantages of quick response time (about 10-9 seconds), small volume, energy saving, low pollution (mercury free), high reliability, capable of mass production, etc. Therefore, the LED can be applied in a wide variety of fields, for example, scanner light sources demanding for a fast response, back lights or front lights of liquid crystal displays (LCDs), illumination for instrument panels of vehicles, traffic signal lamps, and ordinary illuminators.
The conventional LED is mainly made of GaN, and the fabricating method thereof is epitaxy. The LED mainly includes a substrate, a semi-conductive layer, and two external electrodes. The semi-conductive layer further includes two confinement layers having N-type and P-type dopants, and a light-emitting layer located between the two confinement layers. When a forward bias voltage is applied to the external electrode, the current flows through the semi-conductive layer, and electrons and electron holes are combined in the light-emitting layer, thus the light-emitting layer emits light.
The LED is a high power element; 80% of the power is output in the form of heat, and the remaining 20% of the power is output in the form of light energy. Therefore, if the LED package structure is not fitted with an appropriate heatsink, the heat generated will result in the rising of temperature inside, thus affecting the light emitting efficiency of the LED and reducing the service life. Therefore, how to dissipate heat from the high power LED is a task to be solved.
In the U.S. Pat. No. 6,902,291, an in-pavement directional LED luminaire is disclosed. In the luminaire structure, a thermoelectric cooler (TE cooler) is arranged below the LED holder. The TE cooler has a cold end and a corresponding hot end. The cold end of the TE cooler is adjacent to the LED holder and the hot end is attached to a heatsink. As such, the heat generated by the LED can be dissipated by the TE cooler and the heatsink. However, an adhesive agent must be used to assemble the LED holder and the TE cooler, and the TE cooler and the heatsink. Therefore, the process of assembly is quite complicated. When the adhesive agent is heated and expands, the bonding between the LED holder and the TE cooler and between the TE cooler and the heatsink is affected. Thus, the desired heatsinking effect cannot be achieved, and the operation of the LED is affected.